Note: Descriptions are shown in the official language in which they were submitted.
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A MATERIAL SCREENING APPARATUS
TECHNICAL FIELD
The present invention relates to a material screening apparatus for separating
bulk
particulate material into groups of particles of differing sizes.
BACKGROUND ART
A mobile screening apparatus is known whereby the material to be screened is
fed via an
apron feeder which receives and conveys said material onto a horizontal screen
box with
two decks, an upper deck where the largest particles are removed and a lower
deck.
Particles having a smaller size fall through the upper screen deck onto the
lower screen
deck below. At the lower screen deck, particles of the next largest size
grouping are
separated from the remaining smaller particulate matter which falls through
the lower
screen deck.
Elongate conveyers, which are mounted to and extend away from the screening
apparatus, convey the separated materials to three distinct and separate
locations where
they are deposited in stockpiles, according to particle grade.
It is quite common to require five grades of material, namely a reject or
oversized material
and four different grades of screened material. This is achieved by using two
screening
apparatus together in series.
It is therefore an object of all the present invention to alleviate the
disadvantages
associated with the prior art.
SUMMARY OF THE INVENTION
The present invention is more particularly defined in the appended claims
which are
incorporated in this description by reference .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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The invention will hereinafter be more particularly described with reference
to the
accompanying drawings which show, by way of example only, the screening
apparatus of
the invention.
IN THE DRAWINGS:
Figure 1 is a schematic side elevation of a screening apparatus of the prior
art having a
conventional apron feeder and shown in its operating mode;
Figure 2 is a schematic end elevation of a screening apparatus having a
conventional
apron feeder and shown in its operating mode;
Figure 3 is a schematic side elevation of a screening apparatus of the
invention shown in
its operating mode;
Figure 4 is a schematic side elevation of the screening apparatus of the
invention shown
in its stowed mode;
Figure 5a is a schematic plan view of a screening apparatus of the invention
shown on-
site and in its operating mode;
Figure 5b is a schematic plan view of a screening apparatus of the invention
shown on-
site and in an alternative operating mode;
Figure 6a is a schematic plan view of a preferred embodiment of a screening
apparatus of
the invention shown on-site and in its operating mode;
Figure 6b is a schematic plan view of the preferred embodiment of a screening
apparatus
of the invention shown on-site and in an alternative operating mode;
Figure 7a and 7b are isometric illustrations of the preferred embodiment of a
screening
apparatus of the invention shown in its operating mode;
Figure 7c is a detailed illustration of the connection of a conveyor to the
pre-screening
module 50 when in a deployed position;
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Figure 8a is an isometric illustration of the preferred embodiment of a
screening apparatus
of the invention shown in its stowed mode;
Figure 8b is a detailed illustration of the connection of a conveyor to the
pre-screening
module 50 when in a stowed position;
Figure 9a is a schematic illustration of a folding end conveyor of the
preferred
embodiment of a screening apparatus of the invention shown in an operating
mode;
Figure 9b is a schematic illustration of the folding conveyor of the preferred
embodiment
of a screening apparatus of the invention shown in a stowed mode;
Figure 10a is an isometric illustration of a pre-screening module which
comprises a
telescopically movable upper conveyor and is shown in a deployed mode;
Figure 10b is an isometric illustration of a pre-screening module which
comprises a
telescopically movable upper conveyor and is shown in a stowed mode; and
Figure 10c is a detailed side elevation a pre-screening module which comprises
a
telescopically movable upper conveyor and is shown in a retracted mode.
Referring initially to Figure 1 and Figure 2, a mobile screening apparatus 1
of the prior art
comprises a chassis 2 mounted on tracks 2a, a horizontal screen box 3 having
an upper
screen deck 3a and a lower screen deck 3b, a catwalk 6, conveyors 7, 8, 9, a
rear mount
10 and an apron feeder 11.
Bulk material to be screened is fed via apron feeder 11 to the upper screen
deck 3a of
horizontal screen box 3 which separates the largest particles. Movement of the
screen
propagates the large particles remaining on the screen surface towards
conveyor 7 which
conveys them away from the screening apparatus 1 to a remote heap 95, as shown
in
Figure 5a. All particles that are not screened off at this initial stage fall
downwardly
through upper upper screen deck 3a onto the lower screen deck 3b of the
horizontal
screen box 3. At lower screen deck 3b, particles of the next largest size
grouping are
separated from the remaining smaller particulate matter which falls through
the screen.
The particles which are retained by lower screen deck 3b are removed from the
screening
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apparatus 1 via conveyor 8 which conveys them to a remote heap 96, as shown in
Figure
5a. The remaining particles which are sieved off from lower screen deck 3b
fall
downwardly and are transferred via either a chute or a conveyor (not shown) to
conveyor
9 which further conveys them to remote heap 97, as shown in Figure 5a.
Referring now to Figure 3, the mobile screening apparatus 100 of the invention
is shown
in its operating configuration. Components of the apparatus indicated by
reference
numerals 2 through to 10 are common with those of the prior art screening
apparatus 1
shown in Figure 1 and Figure 2. The mobile screening apparatus 100 of the
invention
further comprises a pre-screening module indicated generally by the reference
numeral
50.
The pre-screening module 50 comprises an upper conveyor 51, a lower conveyor
52, an
inclined two-deck screen box 53, a mounting bracket 54, a dual acting folding
ram 55 and
a dual acting lifting ram 56. The two-deck inclined screen box 53 further
comprises an
upper inclined screen 57, a lower inclined screen (not shown) and upper and
lower chutes
58, 59, respectively.
Pre-screening module 50 is pivotally mounted to the screening apparatus 100
via
mounting bracket 54 which is adapted to fit onto rear mount 10 such that the
module 50
can revert from an inclined operational position as shown in Figure 3 to a
horizontal
stowed position as shown in Figure 4 upon actuation of dual acting lift ram 56
which
extends from the rear of the chassis 2 at mounting point 60 to the uppermost
portion of
the two-deck screen box 53. With the dual acting lifting ram 56 extended the
pre-
screening module 50 is tilted about rear mount 10 such that the pre-screening
module 50
can operate at various inclined angles. In an operational position, extension
of dual acting
folding ram 55 deploys upper conveyor 51 which thereby rises above two-deck
screen box
53.
Referring to Figure 3 and Figure 5a, the operation of the mobile screening
apparatus 100
will be described as follows:
Bulk material, which may be in the form of quarried rocks, stones, gravel,
coal, ash or
particulate minerals, is transferred from a crusher 90 or transportation means
onto the
upper conveyor 51 of pre-screening module 50. The bulk material is conveyed
upwardly
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by inclined conveyor 51 until it reaches the uppermost point of the conveyor.
At the apex
of the conveyor's 51 travel, the bulk material drops into the top portion of
the two-deck
screen box 53 before travelling downwardly over upper inclined screen 57 where
at a first
screening stage the largest particles are separated from the bulk material.
5
The inclination of the screen box 53 assists in the separation of and removal
of the large
particles which then exit the rear of the screen box 53 via upper chute 58
before being
transferred by mobile wheeled stockpiler 91 to a heap 94 as shown in Figure
5a. In an
alternative arrangement, shown in Figure 5b, the large particles that exit
upper chute 58
may be fed via mobile-wheeled stockpiler 92 back to a crushing device 90a
which can
reprocess the particles before returning the recycled material via a conveyor
to the
inclined screen 57 for re-screening.
The remaining bulk material falls through the upper inclined screen 57 onto a
lower
inclined screen below (not shown) for a second screening stage whereby
particles in the
next largest size range are separated from the bulk material. Particles which
are unable
to pass through the lower inclined screen exit the rear of the screen box 53
via chute 59
and are then transported by mobile wheeled stockpiler 92 to a heap 93 as shown
in Figure
5a.
The bulk material which has passed through both upper 57 and lower inclined
screens
falls onto continuously moving lower inclined conveyor 52 which elevates to
the upper
screen deck 3a of horizontal screen box 3 on the main mobile screening
apparatus 1 for
further screening as described previously.
Referring to Figures 7a, 7b and Figure 8a, in a preferred embodiment of the
mobile
screening apparatus of the invention, pre-screening module 50 is provided with
a
deploying mechanism that raises the module from a horizontal stowed position
(Figure 8a)
to an inclined operational position (Figures 7a and 7b) using lifts 61 that
extend from
mounting point 62 on chassis 2 to the rear of pre-screening module 50. Raising
lifts 61,
which are actuated by hydraulic lifting rams 61a, causes pre-screening module
50 to tilt
upwardly about rear mount 10 such that the pre-screening module 50 can operate
at
various inclined angles. Upon tilting the pre-screening module 50, lifts 61
also serve to pull
said module rearwards along a plurality of rollers (not shown) provided on
module support
structure 200 so that the upper end of lower inclined conveyor 52 is retained
in relative
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proximity to upper conveyor 5 (shown without conveyor belt) of the horizontal
screen box
3 provided on the main mobile screening apparatus 100 as shown in Figures 7a
and 7b.
Pre-screening module 50 is also provided with a plurality of damping springs
201 which
are required for the vibration function of the apparatus and also help absorb
the impact of
heavy bulk material being loaded onto said module and damp the vibrational
forces
imparted by the module during the initial sequence of pre-screening.
Referring to Figures 7a, 7b and Figures 6a, 6b, in the preferred embodiment,
pre-
screening module 50 is integrally provided with hanging conveyors 910 and 920
(shown
without conveyor belts) which obviate the need for separate mobile wheeled
stockpilers to
transport the pre-screened bulk particulate material from the module 50.
Conveyor 910,
which extends further than conveyor 920, is deployed obliquely from the
support structure
200 of pre-screening module 50 such that the largest particles separated from
the bulk
material may either be conveyed to a separate heap 94 (Figure 6a) or be fed
back to a
crushing device 90a (Figure 6b) where they can be reprocessed before being
returning as
recycled material via a conveyor to the pre-screening module 50 for re-
screening.
With reference to Figures 7a, 7band 8a, hanging conveyors 910, 920, (shown
without
conveyor belts), each comprise a beam 930 that is connected to a universal
joint 931
which is rotatably mounted to the support structure 200 of pre-screening
module 50.
Support spars 932, which are rotatably attached to at one end to support
structure 200 by
means of pivotal hinges 932a connect via pivotal joints 932b to mounting
members 930a
provided on beams 930. Pivotal hinges 932a are vertically and horizontally
offset from
universal joints 931. Hydraulic rams 933 act upon support spars 932 such that
when said
rams are retracted, conveyors 910, 930 are deployed outwardly from mobile
screening
apparatus 100 as shown in Figures 7a, 7b and 7c. Upon extension of hydraulic
ram 933s,
support spars are each rotated about a plane as determined by pivotal hinges
932a and
beams 930 are in turn moved substantially in the direction of rotation of the
support spar
and are thus moved inwardly towards the pre-screening module 50 and are
simultaneously revolved about universal joints 931 so that the stockpilers
910, 920 are
stowed substantially parallel to and vertically against, mobile screening
apparatus 100 as
shown in Figures 8a and 8b, respectively. Flexible linkages 934 which may
comprise
chains, cables or other suitable means extend between beams 930 and the module
support structure 200 to provide additional support to the outwardly extended
conveyors
910, 920 and to locate the conveyor in the optimum working position with the
head drum
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950 of the conveyor in a horizontal position. Further support may be provided
to the
conveyors by means of separately detachable rigid support spars 940 which can
be
connected between beams 930 and the module support structure 200 as shown in
Figures 10a and 10c. Detailed illustrations showing the connection of a
conveyor (910) to
pre-screening module 50 together with the associated linkages in deployed and
stowed
positions are provided in Figures 7c and 8b, respectively.
Conveyors 8 and 9, located on opposing sides of mobile screening apparatus 100
and
shown without conveyor belts in place, each comprise a beam 930 that is
connected to a
universal joint 935 which is rotatably mounted to chassis member 936. Support
spars 937,
938 which extend upwardly from universal joints 937a and 938a attach to the
underside
of beam 930. An hydraulic ram 939 acts on a single support spar of the
respective
conveyors 8, 9 such that extension of said ram causes said support spar to
move the
conveyors 8,9 outwardly from a stowed position (Figure 8a) to a deployed
position
(Figures 7a, 7b and 7c). The provision of rotatably mounted universal joints
931 and 935
enables the respective conveyors 910, 920 and 8,9 to reside within the
confines of
catwalk 6 and rest flat against the sides of mobile screening apparatus 100
thereby
minimising its overall dimensions while in a stowed transportation mode.
With reference to Figure 9a and Figure 9b, to further minimise the overall
dimensions of
mobile screening apparatus 100, in the preferred embodiment end conveyor 7a,
which is
shown without a conveyor belt in place, is of two-part construction and is
provided with a
folding mechanism indicated generally by reference numeral 70 which enables
the
conveyor to fold back on itself. Folding mechanism 70 comprises hydraulic rams
71, 72,
spaced apart lever assembly members 73, linkage arms 73a and support posts 74,
75.
Lever assembly members 73 each comprise a substantially L-shaped member having
a
first limb 73b and second limb 73c. Hydraulic rams 71, 72 each extend upwardly
from
brackets mounted on opposing edges of the rear of mobile screening apparatus
100 and
connect at their respective ends to the respective ends of opposing first
limbs 73b of lever
assembly members 73 at pivot points 730. The respective second limbs 73c of
lever
assembly members 73 are pivotably coupled to the respective sides of the upper
portion
of conveyor 7a at pivot points 76. Linkage arms 73a, are each pivotally
connected
between a lever assembly member 73 at a position proximate the intersection of
first limb
73b and second limb 73c and extend upwardly towards a support post 74, 75 to
which
they are pivotally connected by means of fulcrums 77. This arrangement enables
folding
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mechanism 70 to rotate about support posts 74, 75, upon actuation of hydraulic
rams
71,72. From a deployed position (Figures 7 and 9a) stowing of conveyor 7a
(Figures 8
and 9b) is facilitated by the extension of hydraulic rams 71, 72 which causes
folding
mechanism 70 to revolve upwardly about fulcrums 77 provided on support posts
74, 75,
which in turn induces the rotation of the upper portion of conveyor 7a about
hinges
78which link said upper portion to the lower portion of conveyor 7a. Once the
hydraulic
rams reach their maximum extension, the upper portion of conveyor 7a will have
revolved
about hinges 78 such that said upper portion of conveyor 7a will be inverted
and resting
on top of the upper deck of the screening apparatus as shown in Figures 8a and
9b. From
a stowed position, deployment of conveyor 7a is effected by the retraction of
hydraulic
rams 71,71 causes folding mechanism 70 to revolve downwardly about support
posts 74,
75. The use of such a folding mechanism 70 on conveyor 7a enables the overall
length
and height of the mobile screening apparatus 100 while in a transportation
mode to be
advantageously minimised. Furthermore, the provision of a such a hydraulically
operated
folding mechanism 70 on the underside of conveyor 7a provides additional
robust support
to said conveyor which is particularly advantageous when the mobile screening
apparatus
100 is operating with a conventional apron feeder in place (i.e. in place of
pre-screening
module 50) and whereby the heaviest of the screened material will be conveyed
by this
particular conveyor.
To further minimise the overall length of a mobile screening apparatus 100, in
a further
embodiment the pre-screening module 50 may be provided with an upper conveyor
51a
which is telescopically movable along its longitudinal axis enabling it to
revert from an in-
use extended position to a contacted transport position as shown in Figures
10a and 10b,
respectively. Telescopically movable upper conveyor 51 a comprises an upper
portion 51 c
and a lower portion 51 b, wherein the lower portion 51 b is linearly
extensible relative the
upper portion 51 c to which it is slidably attached. A plurality of rams 80
which extend
between each side of the pre-screening module support structure 200 and the
respective
sides of lower portion 51 b enable said lower portion to move upwardly and
downwardly
along the side rails 51 d of upper portion 51 c. Upon retraction of the rams
80 the lower
portion 51 b is telescopically extended into its operating position as shown
in Figure 10a.
Further retraction of the rams 80 causes the telescopically movable conveyor
51 a to be
raised above the upper inclined screen 57 by means of connecting arms 51 e
which are
pivotably connected between hinged brackets 51f provided on the module support
structure 200 and lifting bar 51g on upper portion 51c. Hinged brackets 51f
also act as a
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stop (as shown in Figure 10c) against the travel of arms 51e thus retaining
the
telescopically movable conveyor 51a at a correct working height above the
upper inclined
screen 57. Movable mounting means provided on the module support structure
support
the underside of telescopically movable conveyor 51a during use and enable
said
conveyor to slide smoothly between operating and transport positions. By way
of example
of a suitable movable mounting means, rollers 81 are shown in the figures.
Following the initial sequence of pre-screening, the particulate material
subsequently
presented to the main screening apparatus 1 is of a finer consistency than
would
otherwise be the case associated with the prior art from one machine.
Furthermore, the
provision of a pre-screening module having a two-deck screen box increases the
versatility of the mobile screening apparatus which is able to provide at
least two
additional grades of screened material while still maintaining its mobility.
The material screening apparatus has a number of unique features:
- a folding mechanism for on board conveyors
- five-way split output for different grades of materials
- combined horizontal and inclined pre-screening module are mounted on the
same
chassis
- oversize material is taken off at the front conveyor and fed back to a
crusher rather
than being fed right through the apparatus
- the entire apparatus can easily be moved with a transport mode so that the
weight,
height and width of the apparatus are within the maximum requirements of the
TUV transport specifications and no special permit is required transport the
apparatus
- the pre-screening module can be removed from, or installed on, the apparatus
depending on the usage requirements in any given situation.
It is thought that the present invention and its advantages will be understood
from the
foregoing description and it will be understood that the invention is not
limited to the
specific details described therein, which are given by way of example only and
that
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various modifications and alterations are possible within the scope of the
invention as
defined in the appended claims.
